High operating temperatures are always a concern when it comes to passive cooling, but here the Tranquil PC defies expectations. We left both the Core i5-equipped Tranquil PC and the identically specified Intel NUC D54250WYK sitting idle for 30 minutes, after which the Abel H2-5 settled at 36°C and the NUC reached 42°C. We then repeated the test with Prime95 pushing the CPU flat out, and while the tables were turned – the Intel topped out at 79°C; the Abel H2-5 at 82°C – the NUC's cooling fan span up to a constant, intrusive whine. The Abel H2-5's chassis did become noticeably hot to the touch, but the temperature remained stable under load and, crucially, it didn't make a peep.